Growth and yield of wheat genotypes in relation to environmental constraints under timely sown irrigated condition

Evaluation of morpho-physiological and yield traits of twenty timely sown irrigated wheat genotypes was done during two seasons (2008–2010). Under the prevailing environmental conditions, the genotypes attained flowering and physiological maturity in about 88–105 and 129–137 days after sowing, respectively. Photosynthesis rate (Pn, μmol m⁻² s⁻¹) was significantly higher in UP 2565 (24.17), while higher rate of transpiration (E, mmol H₂O m⁻² s⁻¹) was observed in UP 2338 (6.17), PBW 226 (6.68) and PBW 509 (6.78). Photosynthesis rate, photosynthetic radiation use efficiency (mol CO₂ mol⁻¹ photon) and apparent carboxylation efficiency (Pn/Ci, μmol m⁻² s⁻¹ μmol⁻¹) declined with temperature above 26°C. An optimum PAR of 1270 μmol m⁻² s⁻¹ was observed. A positive association (r = 0.84**) was observed between total biomass and seasonal radiation use efficiency. Yield performance was significantly higher (5.5–5.7 t ha⁻¹) in DBW 17, HD 2687, HD 2894, PBW 343, PBW 550 and UP 2338, while it was lower (4.6–4.9 t ha⁻¹) in UP 2425, PBW 509, HI 1544 and DBW 16. Grain yield was positively correlated with heat use efficiency and stomatal conductance. Further, the environmental constraints like moderately higher temperatures (above 26°C) affected photosynthesis even under timely sown irrigated conditions in the main wheat producing belt (north western plain zone) of India.